The present invention relates to a thermal analyzer for measuring a signal indicating variations in physical and chemical properties of a sample as a function of sample temperature or time. More particularly, the invention relates to a novel improvement of an apparatus, such as a differential thermal analyzer (DTA) or differential scanning calorimeter (DSC), for measuring the liberation and absorption of heat by a sample, which permits the interchange of thermal analysis data arising from different heating rates of a sample and which, at the same time, allows a thermal analysis of the sample to be performed in a greatly shortened time.
Thermal analysis is an effective means for investigating how material properties vary with temperature. Typical thermal analyzers include differential scanning calorimeters (DSC), differential thermal analyzers (DTA), thermogravimetric measuring apparatuses (TG), thermomechanical analyzers (TMA) and so on, each of which has an objective to measure temperature dependence of various sample quantities of enthalpic balance, differential temperature (qualitative enthalpic balance), weight and length.
In thermal analysis, the physical properties of a sample and temperature variations are continuously measured while heating the sample at a constant rate. In DSC or DTA, heat absorption or liberation in the sample is measured against temperature. The analysis of this kind makes it possible to measure, not only the specific heat of a material, but also the amount of transition heat during fusion or crystallization, and the amount of reaction heat during decomposition or curing, etc.
In the above conventional thermal analysis, it is typical to heat a sample at a heating rate of 5-20 degrees per minute. For example, if a temperature range of about 1000 degrees is scanned, it takes 1 to 3 hours to complete the scan. In this way, the prior art analysis has the disadvantage that the time efficiency is low.
An ordinary thermal analytical apparatus can perform a measuring operation at a heating rate of 50 to 100 degrees per minute, and this shortens the measuring time. Nevertheless, the comparatively low heating rate of 5 to 20 degrees per minute is widely used primarily for the following reason. If a sample inducing plural reactions during scanning of the temperature is heated at a high rate, these reactions tend to overlap. The resulting data is inevitably cumbersome to analyze.
Thermal analysis is intended to investigate the dependence of the physical properties of a sample on temperature. Detailed investigation of the measured signal indicating the physical property has shown that the physical property signal is observed to depend on time as well as on temperature in practice. There are Two main reasons for this, which are:
1) A detector for detecting variations in the physical property of the sample has an intrinsic time constant. PA1 2) The function of temperature is constituted not by a total amount of reactions occurring on a sample but the rate of reaction (reaction ratio per time).
After thermal analysis of a sample is made at a varying heating rate, if measured data are simply taken as physical property values that are functions of temperature, and if they are compared, then results of the measurement are that the same sample shows different decomposition and reaction temperatures reflecting the time dependence effects of the physical property.